This invention relates to valve assemblies, and more particularly to an improved automatic air pressure relief and check valve assembly which, when used in combination with a swimming pool filter tank, automatically opens for permitting air to be evacuated from the tank while the the tank is being filled with water; automatically closes when the tank is full of water for permitting filtration of the pressurized water; and remains closed for preventing air from entering the tank when the water is not pressurized, to prevent the water in the tank from draining until such time when draining is desired.
Most swimming pools include a water recirculation system where water from the pool is circulated through a filter and then returned to the pool. The filter generally comprises a water tank which contains a bed of granular filter material such as sand, or filter elements coated with diatomaceous earth, through which the pool water is forced for removing solid particles from the water. The filtered water is then returned to the swimming pool. Water circulation is conventionally accomplished by means of an electrically driven water pump situated in the water line between the pool and the inlet side of the filter tank, although in some filter systems the pump is situated between the pool and the outlet side of the tank.
Proper maintenance of such filters requires that the tank be disassembled from time to time, for permitting maintenance of the sand bed and cleaning of the diatomaceous earth filter elements. Prior to tank disassembly, of course, the tank must be drained of water.
In swimming pool filter systems of the prior art, a manual air relief valve is conventionally attached to the upper portion of the filter tank. The air relief valve is manually opened to permit air to enter the tank so that the tank may be drained prior to tank disassembly. After the filter has been maintained and the tank reassembled, the maintenance person must assure that the relief valve is open so that air will be permitted to escape from the tank while the tank is being filled with water. When the tank becomes full, the maintenance person must manually close the valve to prevent water from escaping therethrough and to permit recirculating water pressure to be established, as well as for precluding re-entry of air into the tank when the pump is periodically shut down.